Solid-state lighting devices made of light emitting diodes are increasingly useful for applications requiring robustness and long-life. For example, solid-state light emitting diodes (LED) are found today in automotive applications. These devices are typically formed by combining multiple, small LED devices providing a point light source into a single module together with glass lenses suitably designed to control the light as is desired for a particular application (see, for example WO99/57945). These multiple devices are expensive and complex to manufacture and integrate into a single area illumination apparatus. Moreover, LED devices provide point sources of light which are not preferred for area illumination (see for example U.S. Pat. No. 6,305,818).
Organic light emitting diodes (OLEDs) can be manufactured by depositing materials on a substrate. This process enables the creation of single, monolithic lighting elements on a single substrate. The existing art describes the use of electro-luminescent materials as adjuncts to conventional lighting (for example U.S. Pat. No. 6,168,282 “Electro-Luminescent lighting Arrangement for a Lighting Apparatus with a Lamp Holder” granted to Chien). In this case, the electro-luminescent material is not useful for primary lighting. EP1120838A2 describes a method for mounting multiple tiles on a mounting substrate to create large arrays of illuminators. However, this is complex and expensive and is not necessary for some applications.
It is also important that lighting devices in common use by consumers be compatible with the existing lighting infrastructure, for example the common screw-type base known in the US and the pin-type bayonet bases used in Europe. Moreover, the lighting devices must be readily and safely replaced by consumers at minimal cost.
Applications for OLED devices in area illumination are constrained by cost. The traditional way of providing power to OLED devices using conventional power supplies are too expensive for illumination applications. Techniques used for traditional inorganic, point-source LED devices are not suitable as they do not supply, for example, reverse bias to prolong the useful life of an OLED device.
There is a need therefore for replaceable OLED area illuminators having a simple construction, low cost, and compatibility with the existing lighting infrastructure.